Of course,
these little gems have to be
different than other fruit flies. The females have a sclerotized (hardened)
serrated ovipositor, (egg-laying structure) just right for laying eggs in intact, still-ripening fruit. They couldn’t be like their relatives who are more interested in
fallen or overripe fruit, no!

What’s so
disgusting about the whole thing is that the larvae rapidly turn raspberries
into a liquid mess. One morning, a staff member collected a small bag for a snack later in the day. When she went to eat them, the now liquefied fruit was infested
with tiny white maggots.

Liquified raspberries with maggot (just above center)

While they
will damage many types of small fruit, peaches and cherries, they prefer the
volatiles of raspberries. To add insult to injury the insects feed on other soft-
fleshed fruit found in our landscape – elderberries, chokecherries, mahonia and
honeysuckle. So there’s plenty of food to keep them hanging around, even if
it’s not their favorite!

We first
found SWD late last summer and began a sanitation program: keeping fruit
regularly picked and collecting fallen fruit from the ground. We started a
trapping program in July using a yeast-sugar water bait placed in red-lidded
empty peanut butter jars. (Thanks to my dedicated family for eating all the
peanut butter!) While we’ve collected mostly
male and female SWDs, it is interesting to see who else likes the bait. So far, we’ve also collected sap bugs, earwigs and other fruit flies.

Trap for SWD

This year
we’re using sanitation and trapping to monitor the population and sort-of manage it.
Being a garden on public property that can be accessed virtually any time of
day, we’re a bit reluctant to introduce pesticides.

One of the
benefits of the infestation is that we have a living laboratory for training
our volunteers. The clinicians will also
be able to identify the adults after an upcoming workshop, so they can better
assist customers.

And frankly,
when I check the raspberry fruit I am amazed at how many thrips are wandering around in them. I wonder how many I've consumed over the years. Maybe I should just view SWD in the same way –
extra protein, anyone?

3 comments:

Great article Mary! Eat them immediately... or refrigerate... or freeze and eat later. Yes, it's probably not a good idea to think about how many thrips and other insects one eats with produce (without harm, by the way).

Use a lid that the drosophila cannot get through...like a No-See-Um fabric or other very fine mesh. If there's a lid that comes with your cup, that will work too (think of a fast food cup). Link to Cornell Extension's publication: http://www.fruit.cornell.edu/spottedwing/pdfs/SWDTraps_CornellFruit.pdf